This invention relates to a method of preparing improved mold release agents for foamed rubber manufacture; more particularly the invention describes the use of said improved mold release agents in the manufacture of urethane foamed rubber products.
The industry has expended considerable time and efforts in trying to develop materials to facilitate the release of molded resins from the mold. In general, each molding composition requires a special release material or agent and many times, a different release agent is required with the various foams. In many cases, hydrocarbon waxes in the forms of low melting solids, dispersions or solutions which are applied to the mold surfaces by wiping or spraying have proved quite satisfactory if the wax is sufficiently insoluble in the molding or casting composition that the formed article would not adhere well to the wax surface. In the manufacture of automotive crash pads which are fabricated from two components, a foamed rubber core and a vinyl plastic outer skin, it has been found that the foam adheres tenaciously to the metal mold and a mold release agent is applied around the edges and openings in the covering to prevent the foam from sticking to its outside surface during fabrication. About 1/4 lb. of mold release agent is also applied to the metal mold, usually during the manufacturing process for each of the crash pads. It is applied onto the form prior to adding the liquid resin mix. During the curing period, the foamed rubber expands to fill the required space between the vinyl and the metal form. The completed crash pad is then withdrawn from the mold and the release agent is removed by means of a solvent from the outer vinyl skin. This operation is generally done by hand. In the prior art, workers have employed as a mold release agent a 50--50 Estan/Varsol composition, but Varsol is now precluded because of safety reasons. Other workers have found that Fluorine containing silane derivatives are useful as mold release agents. However the cost of these items limits their use in the manufacture of automotive crash pads. Silicones have also been found to be good release agents, but unfortunately stain the vinyl skin covering. Another prior art worker has employed an estersil gel base in an evaporable vehicle.
This is sprayed or painted on the mold; but, such a vehicle requires the use of hydrocarbon solvents. It is therefore an object of this invention to define a mold release agent which will permit the efficient removal of the finished product from the mold and at the same time would be water soluble to allow the removal of the mold release agent from the molded product by spraying or washing. It is another object of this invention to provide a method of manufacturing these improved mold release agents. These and other objects will become evident from the following description and discussions of the preferred embodiments.